1. Field of the Invention
The present invention relates to an air conditioner, and particularly, to an apparatus and a method for controlling oil of an air conditioner.
2. Description of the Prior Art
In general, an air conditioner cools warm air or heats cool air in a room. Hereinafter, a construction of an air conditioner having two compressors in accordance with a conventional art will now be described with reference to FIG. 1. Herein, the two compressors are selectively operated according to a cooling load of a room.
FIG. 1 is a block diagram showing a construction of an air conditioner having two compressors in accordance with the conventional art.
As shown therein, an air conditioner having two compressors includes a first compressor 18A and a second compressor 18B selectively operated according to a cooling load of a room to vary compressing capacity; a condenser 1 for radiating heat of a refrigerant compressed by the first and second compressors 18A, 18B; an expansion valve 2 for expanding the refrigerant discharged from the condenser 1; and an evaporator 3 receiving the refrigerant expanded by the expansion valve 3 and generating cool air. Assuming that the first compressor 18A is a compressor of small compressing capacity and the second compressor 18B is a compressor of high compressing capacity, the construction of the air conditioner having the two compressors will now be described.
First, suction pipes 9, 13 respectively connected to the first compressor 18A and the second compressor 18B are connected by hoses 5, 7 diverged from a suction hose 4 connected to the evaporator 3. In addition, discharge pipes 11, 14 respectively connected to the first compressor 18A and the second compressor 18B are connected by hoses 10, 16 diverged from a discharge hose 17 connected to the condenser 1.
To the diverged hoses 5, 7, 10, 16 are respectively connected suction valves 6, 8 and discharge valves 12, 15 which are selectively opened/closed by hand or a control means such as a microcomputer or the like.
Accordingly, the air conditioner having the two compressors controls a cooling cycle by operating the first compressor 18A or/and the second compressor 18B according to the cooling load. That is, capacities of the compressors are changed in such a manner than the air conditioner operates only the first compressor 18A when an indoor cooling load is small, operates only the second compressor 18B when the indoor cooling load is large, and operates both the first and second compressors 18A, 18B when the indoor cooling load is maximum.
When a refrigerant is compressed by the first compressor 18A and/or the second compressor 18B, refrigerating machine oil in the first and second compressor 18A, 18B is mixed with the refrigerant to perform a cooling cycle and then is sucked into the first and second compressors 18A, 18B via an accumulator (not shown).
Recently, an air conditioner having four compressors has been used. General operations of the air conditioner having four compressors are the same as those of the air conditioner of FIG. 1. The four compressors may be designed to have the same compressing capacity or may be designed to have different compressing capacities.
However, when the four compressors are operated according to the conventional art, most of refrigerating machine oil is sucked into a certain compressor, thereby causing insufficiency of refrigerating machine oil in other compressors. That is, the amount of the refrigerating machine oil collected in a common accumulator is slightly different depending on suction pipe laying and performance variations of the compressors. In case of simultaneously operating four compressors for many hours, refrigerating machine oil in compressors is not uniform, thereby causing damage of compressors having insufficient refrigerating machine oil.
An air conditioner having a multi-compressor in accordance with the conventional art is disclosed in detail in U.S. Pat. No. 6,519,957 issued in Feb. 18, 2003.